Visible-Light Photoredox-Catalyzed Amidation of Benzylic Alcohols

Catalyst-Free Photooxidative N-Acylation of Azoles with Aldehydes

A catalyst-free photochemical N-acylation of azoles with aldehydes has been developed using inexpensive BrCCl3 as the oxidant. This transition-metal- and photocatalyst-free amidation proceeded efficiently with a wide variety of substrates to give the corresponding N-acylazoles, including for the late modification of pharmaceutically active molecules, and on a gram-scale.

Visible light-driven molecular oxygen activation for oxidative amidation of alcohols using lead-free metal halide perovskite

Herein, we report the modulation of the band structures of halide perovskite Cs2CuBr4 by tuning the synthesis methods. The photocatalyst PC-1, synthesized by the hot injection method, has a more negative conduction band minima (CBM) than the photocatalyst PC-2, synthesized at room temperature. As a result, PC-1 can activate molecular O2 more efficiently to initiate the radical-mediated dehydrogenation of alcohols. The more positive valence band maxima (VBM) of PC-1 also facilitates amine oxidation to the corresponding radical. Further, improved charge separation and transport and a decrement in the photogenerated charge carrier recombination have been detected for PC-1 to enhance photocatalytic activity. PC-1 showed improved yields for a series of structurally diverse amides (highest yield = 98%) by oxidative amidation of alcohols under visible light irradiation.

One-Pot Oxidative Amidation of Aldehydes via the Generation of Nitrile Imine Intermediates

A one-pot procedure for the oxidative amidation of aldehydes via the in situ generation of reactive nitrile imine (NI) intermediates has been developed. Distinct from our progenitor processes, mechanistic and control experiments revealed that the NI undergoes rapid oxidation to an acyl diazene species, which then facilitates N-acylation of an amine. A range of substrates have been explored, including application in the synthesis of pharmaceutically relevant compounds.

Synthesis and characterization of nanocatalyst Cu2+/mesoporous carbon for amidation reactions of alcohols

In this research, mesoporous carbon (MC) with high efficiency (0.65 g yield from 1.0 g MCM-41 and 1.25 g sucrose) was successfully prepared by adding carbon precursor (sucrose) in a single step with ultrasonic waves, which reduces time and energy cost. Then, the Cu²⁺/Mesoporous carbon nanocatalyst (Cu²⁺/MC) was synthesized by adding Cu(NO₃)₂ in a single step and applied as a catalyst in amidation reactions of alcohols. Also, Cu²⁺/MC was characterized using different spectroscopic methods and techniques, including Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), N₂ adsorption analysis (BET), X-ray diffraction analysis (XRD), Energy Dispersive X-ray (EDX), and Thermogravimetric Analysis (TGA). Moreover, to show the catalytic merits of Cu²⁺/MC, various primary and secondary amines and ammonium salts were applied in the amidation of alcohols. Easy synthesis method, recyclability, excellent yields (80-93%), and simple work-up are some noticeable strengths of using Cu²⁺/MC as a catalyst in this reaction.

Visible Light-Mediated Carbamoylation of para-Quinone Methides

We report a photocatalytic approach for the installation of the amide moiety onto para-quinone methides. This transformation features a net reductive approach for the generation of carbamoyl radicals from amide-substituted Hantzsch ester derivatives under transition metal-free conditions. This protocol exhibits wide scope and allows access to diarylacetamides employing a C-C bond formation approach.

Progress in C-C and C-Heteroatom Bonds Construction Using Alcohols as Acyl Precursors

Acyl moiety is a common structural unit in organic molecules, thus acylation methods have been widely explored to construct various functional compounds. While the traditional Friedel-Crafts acylation processes work to allow viable construction of arylketones under harsh acid conditions, recent progress on developing acylation methods focused on the new reactivity discovery by exploiting versatile and easily accessible acylating reagents. Of them, alcohols are cheap, have low toxicity, and are naturally abundant feedstocks; thus, they were recently used as ideal acyl precursors in molecule synthesis for ketones, esters, amides, etc. In this review, we display and discuss recent advances in employing alcohols as unusual acyl sources to form C-C and C-heteroatom bonds, with emphasis on the substrate scope, limitations, and mechanism.

Recent Advances in Visible-Light-Mediated Amide Synthesis

Visible-light photoredox catalysis has attracted tremendous interest within the synthetic community. As such, the activation mode potentially provides a more sustainable and efficient platform for the activation of organic molecules, enabling the invention of many controlled radical-involved reactions under mild conditions. In this context, amide synthesis via the strategy of photoredox catalysis has received growing interest due to the ubiquitous presence of this structural motif in numerous natural products, pharmaceuticals and functionalized materials. Employing this strategy, a wide variety of amides can be prepared effectively from halides, arenes and even alkanes under irradiation of visible light. These methods provide a robust alternative to well-established strategies for amide synthesis that involve condensation between a carboxylic acid and amine mediated by a stoichiometric activating agent. In this review, the representative progresses made on the synthesis of amides through visible light-mediated radical reactions are summarized.

Acetylation of alcohols and amines under visible light irradiation: diacetyl as an acylation reagent and photosensitizer

An unprecedented strategy for the acetylation of alcohols and amines using diacetyl as both an acylation reagent and a photosensitizer was well developed.

Green and Sustainable Visible Light-Mediated Formation of Amide Bonds: An Emerging Niche in Organic Chemistry

Amide bond is one of the most fascinating functional groups in nature due to its stability, conformational diversity, high bond polarity, and abundance in numerous natural products and drug candidates,...

Zirconium oxo clusters as discrete molecular catalysts for the direct amide bond formation

A discrete dodecanuclear Zr oxo cluster catalyzed the direct formation of amide bonds without the need of water scavenging or dry reactions conditions showcasing the potential of these molecular clusters to become a new class of efficient catalysts.

Cage-like manganesesilsesquioxanes: features of their synthesis, unique structure, and catalytic activity in oxidative amidations

A family of Mn-based cage-like silsesquioxanes (and complexes with 1,10-phenanthroline) exhibits unique types of molecular architectures and catalytic activity in oxidative amidation reactions.

Visible Light-Driven and Singlet Oxygen-Mediated Photochemical Cross-Dehydrogenative C3-H Sulfenylation of 4-Hydroxycoumarins with Thiols Using Rose Bengal as a Photosensitizer

A visible light (white light-emitting diode/direct sunlight)-driven photochemical synthesis of a new series of biologically interesting 3-(alkyl/benzylthio)-4-hydroxy-2H-chromen-2-ones has been achieved through a cross-dehydrogenative C₃-H sulfenylation of 4-hydroxycoumarins with thiols at ambient temperature in the presence of rose bengal in acetonitrile under an oxygen atmosphere. The notable features of this newly developed method are mild reaction conditions, energy efficiency, metal-free synthesis, good to excellent yields, use of low-cost materials, and eco-friendliness.

Iron-Catalyzed α-C-H Cyanation of Simple and Complex Tertiary Amines

This manuscript details the development of a general and mild protocol for the α-C-H cyanation of tertiary amines and its application in late-stage functionalization. Suitable substrates include tertiary aliphatic, benzylic, and aniline-type substrates and complex substrates. Functional groups tolerated under the reaction conditions include various heterocycles and ketones, amides, olefins, and alkynes. This broad substrate scope is remarkable, as comparable reaction protocols for α-C-H cyanation frequently occur via free radical mechanisms and are thus fundamentally limited in their functional group tolerance. In contrast, the presented catalyst system tolerates functional groups that typically react with free radicals, suggesting an alternative reaction pathway. All components of the described catalyst system are readily available, allowing implementation of the presented methodology without the need for lengthy catalyst synthesis.

Amine hydrochloride salts as bifunctional reagents for the radical aminochlorination of maleimides

Amine hydrochloride salts have been typically used as amination reagents.